This study initiates an investigation of transmission at the first synapse of the baroreceptor reflex. The synapse is located in an area of the medulla which is composed of cells of the medial, dorso-medial and dorso-lateral nuclei of the solitary tract. This area receives afferents from the baroreceptor pathways as well as from many other central nervous system areas and is a major site of cardiovascular integration. The focus of this project will be a characterization of the electrical and pharmacological properties of the neurons in this area. In these studies, the cells are isolated enzymatically. We have developed this preparation which provides, for the first time, the opportunity to study the properties of individual cells involved in cardiovascular regulation. The patch clamp technique for whole cell recording will be used to determine the ionic currents responsible for the membrane potentials and to examine the responses to putative transmitter substances and to such drugs as clonidine and the calcium antagonists. This will provide information concerning which substances are involved in regulating the neural activity and what mechanisms are used. The cells will also be characterized using immunocytochemical techniques. The properties of the cells from normotensive rats (WKY strain) will be compared with those from spontaneous hypertensive rats (SHR). The studies will serve as a foundation for future studies examining the processing of baroreceptor information by these second order neurons.